USG FLEX 200H (uOS 1.39): DDNS Effective IP is always the Backup address, even though the Primary in

baba

Hi all,

the DDNS address failover doesn't pick the primary IP address.

Environment

• Device: USG FLEX 200H
• Firmware: V1.39

Problem

• The Effective IP in the DDNS status is always the Backup (Public IP) address.
• The Primary interface is up and reachable: link up, IP assigned, internet traffic goes through it, and the interface shows as connected in [Monitor / Interface status].
• It stays on Backup and never switches back to Primary, even after a reboot or after re-applying the profile.

What I'd expect
While the Primary interface is up, the Effective IP should be the Primary interface IP. The Backup should only be used when the Primary interface goes down.

Already tried

• Re-created the DDNS profile
• Primary = Interface with no Backup: "Effective IP is then correct"

Questions

1. How does the device decide that the Primary interface is "available"? Connectivity check at interface is already enabled.
2. Is this a known bug in 1.39?
3. Is there a CLI command to show the DDNS failover state and why the Backup was selected?

Thanks!

Maverick87

Hi @baba,

probably it's the same problem here:

https://community.zyxel.com/en/discussion/34210/primary-wan-not-returning-after-connectivity-failure-on-flex-200h

If the Primary WAN not returning after a connectivity failure, you stay always on backup.

baba

Fixed in V1.39(ABWV.0)ITS-26WK37-m12845

Zyxel_Tina

[Update]

The fix has been included in the latest firmware, v1.40.

nielsscheldeman

https://community.zyxel.com/en/discussion/comment/87762#Comment_87762

Thank you, will schedule the upgrade.